Innovative Approach for MGP and Heavy Oil Contaminant Remediation

摘要

An innovative sequential in-situ treatment process has been developed to economically reduce the total contaminant mass of viscous heavy oils and PAHs at Manufactured Gas Plant (MGP) sites. The first step is to reduce the viscosity of the contaminants by injecting a biodegradable terpene co-solvent. The second step further reduces the viscosity and molecular weight of the contaminants by the application of an aggressive in-situ chemical oxidant (activated persulfate). Exothermic free radical chemistry can be applied to thermally reduce viscosity and molecular weight of heavy oils and polynuclear aromatic hydrocarbons (PAHs). This will increase aqueous phase solubility and free product mobility for the enhancement of free-product recovery and enable in-situ chemical oxidation of the dissolved heavy oils at MGP sites. The application of a biodegradable co-solvent applied to the heavy oils effectively dissolves the contaminant mass without using the inefficient thermal desorption of the mass through the use of steam or catalyzed peroxide alone. Once the contaminant mass has been desorbed from the soil matrix, it then can be recovered by groundwater hydraulic mounding (free-product push techniques). The first two process steps reduce source area toxicity by desorbing and treating the total contaminant mass within the soil matrix. The exothermically produced persulfate free radicals that are generated can remain activated and capable of oxidizing residual contaminant mass for over a month. Sodium persulfate can be activated with a transition metal catalyst, hydrogen peroxide, and by raising the groundwater temperature.The installation of a thermocouple in every chemical injection well and monitoring well can provide useful persulfate activation process control data. Wireless radio frequency transmitters can be used to collect the realtime temperature data from the thermocouples on-site. A laptop computer equipped with a wireless modem on-site can then transmit this data electronically via the information superhighway to an off-site computer equipped with a web-based Smart DataSM software information package to provide three-dimensional images of the data in a timely manner thus allowing efficient and effective field optimization of the chemical oxidation treatment process. Three-dimensional images enable the field technicians to adjust chemical oxidant and conditioning reagent injection flow rates. Groundwater temperature and the in-situ activation of persulfate can thus becontinuously optimized. Key benefits include process safety management via avoidance of potential run away exothermic reactions, reduction in chemical and in-situ groundwater heating costs and of course minimization of field technician labor.